It is hard to see how the case handled by the second sentence under the first bullet doesn't include the case stated in the second bullet.
The only difference is that in the second bullet the information is asked for in a label, and in the first case in a "text equivalent." In either case the actual requirement is that this minimal information about the non-text context item is required to be available in a way that the user knows it is about the non-text item.
The fact that information in a label need not be replicated in a substitutable text object is true here and is a vest-pocket example of equivalent facilitiation.
merge two items under the pattern of "human-understandable text explanation associated with the non-text object by a programmatically determined (i.e. machine recognizable) association."
Thank you for your comment. We have modified 1.1.1 as follows:
1.1.1 Non-text Content: Except for the situations listed below, a text alternative that presents equivalent information is provided for all non-text content.
* Controls-Input: If non-text content is a control or accepts user input, then it has a name that describes its purpose. (See also Guideline 4.1 Support compatibility with current and future user agents, including assistive technologies)
* Media-Test-Sensory: If non-text content is multimedia , live audio-only or live video-only content, a test or exercise that must be presented in non-text format , or primarily intended to create a specific sensory experience , then text alternatives at least identify the non-text content with a descriptive text label. (For multimedia, see also Guideline 1.2 Provide synchronized alternatives for multimedia.)
* CAPTCHA: If the purpose of non-text content is to confirm that content is being accessed by a person rather than a computer, then text alternatives that identify and describe the purpose of the non-text content are provided and alternative forms in different modalities are provided to accommodate different disabilities.
* Decoration-Formatting-Invisible: If non-text content is pure decoration, or used only for visual formatting, or if it is not presented to users, then it is implemented such that it can be ignored by assistive technology.